Browsing by Author "Carvalho, A.P."
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- Effects of dietary exposure to herbicide and of the nutritive quality of contaminated food on the reproductive output of Daphnia magnaPublication . Silva, M. Bessa da; Abrantes, N.; Rocha-Santos, T.A.P.; Duarte, A.C.; Freitas, A.C.; Gomes, A.M; Carvalho, A.P.; Marques, J.C.; Gonçalves, F.; Pereira, R.Risk assessment of pesticides has been based on direct toxic effects on aquatic organisms. Indirect effects data are taken into account but with limitations, as it is frequently difficult to predict their real impacts in the ecosystems. In this context the main aim of this work was to assess how the exposure to the herbicide pendimethalin (Prowl®), under environmentally relevant concentrations, may compromise the nutritional composition of food for a relevant group of primary consumers of freshwater food webs—the daphnids, thus affecting their reproduction performance and subsequently the long-term sustainability of active populations of this grazer. Therefore, Daphnia magna individuals were chronically exposed in a clean medium to a control diet (NCF – i.e., non-contaminated green algae Raphidocelis subcapitata) and to a contaminated diet (CF – i.e., the same monoalgal culture grown in a medium enriched with pendimethalin in a concentration equivalent to the EC20 for growth inhibition of algae), during which reproductive endpoints were assessed. The algae were analysed for protein, carbohydrate and fatty acid content. The chemical composition of R. subcapitata in the CF revealed a slight decrease on total fatty acid levels, with a particular decrease of essential !9 monounsaturated fatty acids. In contrast, the protein content was high in the CF. D. magna exposed to CF experienced a 16% reduction in reproduction, measured as the total number of offspring produced per female. Additionally, an internal pendimethalin body burden of 4.226 "g g−1 was accumulated by daphnids fed with CF. Hence, although it is difficult to discriminate the contribution of the pesticide (as a toxic agent transferred through the food web) from that of the food with a poor quality—compromised by the same pesticide, there are no doubts that, under environmentally relevant concentrations of pesticides, both pathways may compromise the populations of freshwater grazers in the long term, with consequences in the control of the primary productivity of these systems.
- Effects of proteolytic digestion on the cyanotoxins microcystin-LR and cylindrospermopsin: the importance in integrating the bioaccessibility in human health risk assessmentPublication . Freitas, Marisa; Azevedo, J.; Carvalho, A.P.; Mendes, V.M.; Manadas, B.; Campos, A.; Vasconcelos, V.The occurrence and proliferation of toxic cyanobacterial blooms are an emergent environmental concern worldwide. Microcystin-LR (MC-LR), a potent hepatotoxin, is the most documented and studied cyanotoxin. The cytotoxin cylindrospermopsin (CYN) has been recognized of increased concern due to the invasive nature of its main producer, Cylindrospermopsis raciborskii. Previous studies have shown that edible aquatic organisms, especially bivalves, can accumulate high levels of these cyanotoxins. MC-LR and CYN are stable at a wide range of temperatures and pHs, thus the knowledge of the influence of human digestion on its concentration in food is required to achieve a more accurate health risk assessment. The aim of this study was to assess the MC-LR and CYN bioaccessibility in edible bivalves. Clams (C. fluminea) fed MC-LR-producing M. aeruginosa and mussels (M. galloprovincialis) fed CYN-producing C. raciborskii were subjected to an in vitro digestion model adapted from Maulvault et al. (2011) and Versantvoort et al. (2005). Bioaccessibility of MC-LR and CYN were then assessed by LC-MS/MS. The bioaccessibility of MC-LR after proteolytic digestion was reduced to 83%, potentially because of its degradation by pancreatic enzymes. The in vitro digestion with salivary and gastrointestinal juices considerably decreased the CYN availability in uncooked and steamed mussels. Our results suggest that risk assessment based on MC-LR and CYN concentration in raw products might not be representative of true human exposure, once bioaccessibility strongly reduces the potential toxicological risks. Thus, the incorporation of the bioaccessibility of these cyanotoxins in the human exposure estimation would be of particular relevance to the application of more forceful management measures.